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This article in SSSAJ

  1. Vol. 35 No. 2, p. 265-269
    Received: Aug 3, 1970
    Accepted: Dec 28, 1970

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The Metal Complexing Capacity and the Nature of the Chelating Ligands of Water Extract of Poultry Litter1

  1. K. H. Tan,
  2. R. A. Leonard,
  3. A. R. Bertrand and
  4. S. R. Wilkinson2



The metal complexing capacity and the nature of the chelating ligands of organic matter extracted from broiler house litter were studied by ion-exchange equilibrium and dissolution methods and infrared spectroscopy.

The water extract of broiler house litter appeared to exhibit a significant chelating effect on the cations Cu2+, Zn2+, Mg2+, and Al3+. The amount of organic matter complexed by one mole of metal and the stability of metal complexes increased with increasing pH in the cases of Cu-, Mg-, and Al-complexes, but were unaffected by changes in pH in the case of Zn-complexes. With respect to the divalent ions, the amount of organic matter chelated and the stability of the divalent metal-complexes decreased in the order Cu > Zn > Mg.

Dissolution studies with insoluble Al2O3 and Fe2O3 powders showed that both Al and Fe were chelated in the aqueous extract, but 10 times more Al than Fe was dissolved in a given time period.

Infrared analysis revealed spectrograms of the ligands similar to those obtained for polysaccharides. However, since the freeze-dried extract contained 9% N, some NH2 groups must have been present, although bands of these groups were not resolved from overlapping O-H bands. Functional group frequency vibration comparisons at 3,500, 3,200, 1,650, and 1,400 cm-1 showed that the formation of stable metal-complexes involved carboxyl electrovalent linkages and probably hydroxyl and/or amino coordinate linkages.

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